Methods and apparatus for stroke patient treatment

ABSTRACT

Methods and apparatus for assessing the condition of and treating patients for stroke during the delivery of continuous positive airway pressure (CPAP) are disclosed. By determining central and obstructive apnea occurrences or the percentile of pressure delivered to the patient from patient airflow, stroke indicators may be calculated and analyzed to provide information on the type of stroke a patient has suffered and the degree of a patient&#39;s neuro-recovery. The apparatus may be programmed with a particular protocol intended to identify between alternative forms of CPAP treatment appropriate for the patient based upon an assessment of the patient&#39;s condition. The device can select and recommend between the various treatment forms, identify billing reimbursement codes and generate data to track patient response to stroke treatments.

This application is a continuation of application Ser. No. 10/450,068filed on Dec. 16, 2003 now U.S. Pat. No. 7,018,341, now allowed, whichis a National Stage Application of International Patent Application No.PCT/AU01/01595 filed on Dec. 11, 2001, which claims the priority filingdate of U.S. Provisional Patent Application Ser. No. 60/254,151 filed onDec. 11, 2000. U.S. application Ser. No. 10/014,684 filed Dec. 11, 2001,now U.S. Pat. No. 6,832,609, also claims priority of ProvisionalApplication No. 60/254,151.

FIELD OF THE INVENTION

The invention relates to methods and apparatus for diagnosing, managingand treating stroke patients both as in-patients and out-patients.

BACKGROUND OF THE INVENTION

Stroke, or brain attack as it is commonly called, can be caused byeither vascular hemorrhage or vascular blockage with the latteraccounting for about 80% of the events which lead to a stroke. Vascularhemorrhage is also termed a haemorrhagic stroke or an aneurism. Vascularblockage may also be termed ischaemic stroke. Both types of stroke areassociated with considerable morbidity in terms of long-termneurological deficit and the risk of subsequent stroke as well asmortality post stroke.

Stroke treatment in the acute phase typically entails the invasiveadministration of clot dissolving drugs within the first three hours ofthe stroke as well as stabilization of cardiovascular functions andvital signs. After treatment in the acute phase, patients may typicallyfollow four pathways: (i) in the case of mild stroke the patient may gohome, (ii) in the case of a more severe stroke where it is believed animprovement in outcome can occur the patient may be sent torehabilitation, (iii) other patients may be sent to special care/nursinghome, (iv) some patients die. The present application is concerned withpatients in the rehabilitation pathway. Rehabilitation is costly forhealth care systems hence it is desirable to provide improved patientoutcomes at a lower cost where possible.

While the use of a blood thinning agent such as Tissue PlasminogenActivator may be used in the treatment of ischaemic stroke, it may bethe wrong therapy to give in the case of a haemorrhagic stroke. Hence itis important to determine the type of stroke which has occurred in thepatient. Furthermore, the drug therapy may vary during the course oftreatment depending on the progress which the patient makes. Hence it isimportant to monitor the progress of the patient during treatment.

The application of nasal Continuous Positive Airway Pressure (“CPAP”) asa treatment for Obstructive Sleep Apnea (“OSA”) was invented by Sullivanand taught in U.S. Pat. No. 4,944,310. That patent described continuouspositive airway pressure being applied to a patient, through thepatient's nares, to treat breathing disorders, including sleep apnea. Ithas been found that the application of pressure which exceedsatmospheric pressure, typically in the range 4 to 15 centimeters of H₂Ois useful in treatment. OSA is an example of a broader class ofbreathing disorders generally referred to as Sleep Disordered Breathing(“SDB”).

In one form, nasal CPAP treatment of OSA involves the use of a computercontrolled blower, such as the AUTOSET T™ device available from ResMedLtd., to provide a supply of air or breathable gas at pressures in therange of 4 to 20 cm H₂O to the airway of a patient via a mask. Examplesof suitable nasal CPAP masks are the MIRAGE™ nasal mask and the MIRAGE™full face mask also available from ResMed Ltd. The AUTOSET T™ devicecontinuously monitors the state of the patient's airway and determinesan appropriate pressure to treat the patient, increasing it ordecreasing it as necessary. Some of the principles behind the operationof the AUTOSET T™ device are described in U.S. Pat. No. 5,704,345.

Another form of treatment for SDB is bi-level pressure supportventilation provided by way of a nasal CPAP mask. The treatment involvesproviding air at a higher pressure during the inspiratory portion of thebreathing cycle and at a lower pressure during the expiratory portion ofthe breathing cycle. A suitable device for delivering bi-level nasalCPAP is the VPAP™ II ST/A available from ResMed Ltd.

A typical clinical pathway for OSA is as follows:

-   -   (i) A patient consults their general practitioner or physician;    -   (ii) The general practitioner or physician refers the patient to        a specialist or a sleep clinic;    -   (iii) The specialist or clinic assesses the patient;    -   (iv) An overnight polysomnography is performed;    -   (v) An overnight titration study is performed.        In a hospital setting, the team of physicians treating        inpatients for other conditions may recognize symptoms of sleep        disordered breathing on an ad hoc basis and refer the inpatient        to a sleep specialist within the hospital. The patient will then        proceed through steps (iii) to (v) as above.

Recently it has become recognized that stroke patients may benefit fromtreatment with CPAP, for example as taught in International PatentApplication WO98/51362 (Farrell & Pace). While the clinical pathways foridentifying patients with OSA are becoming more established, there arefew clinical pathways for identifying stroke patients who may benefitfrom such therapies. Furthermore, there are no known devices formanaging the therapy of such patients.

It is an objective of the invention to provide methods and apparatus formanaging the treatment of respiratory disorders in stroke patients. Itis a further objective to provide methods and apparatus which assist inthe identification or diagnosis of stroke patient condition to assist intreatment of the patient.

SUMMARY OF THE INVENTION

The invention provides methods and apparatus for managing ventilatorytreatment of stroke patients. In one form, the invention providesapparatus for diagnosis, patient monitoring, nasal ventilation, with orwithout concomitant drug therapy, using continuous positive airwaypressure (CPAP) or bi-level pressure treatment or variants thereof,including devices which automatically set their pressures based onphysiologic data inputs.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows apparatus according to the invention;

FIG. 2 shows a first in-patient flowchart according to the invention;

FIG. 3 shows a second in-patient flowchart according to the invention;

FIG. 4 shows a third in-patient flowchart according to the invention;

FIG. 5 shows a first out-patient flowchart according to the invention;

FIG. 6 shows a second out-patient flowchart according to the invention;

FIG. 7 shows a flow chart in accordance with an embodiment of theinvention.

DESCRIPTION OF THE INVENTION

Nasal CPAP treatment has been traditionally used for the management ofpatients with obstructive sleep apnea where CPAP acts as a pneumaticsplint to maintain upper airway patency and therefore ensures free flowof air while the patient sleeps. The current invention describes the useof positive pressure ventilation, which may include CPAP, bi-levelpressure, or variants thereof, for stroke patients. The use of CPAPtreats stroke patients by improving arterial blood oxygenation levelsand reducing arterial carbon dioxide levels as well as improvingauto-regulation of, for example, blood pressure, cardiac output andventilation. Improvements in morbidity, such as rate and degree ofrecovery of vital signs and patient stabilization in the acute phase, isan expected benefit. Also, an improvement in neurological deficits inthe short and/or long term is an expected benefit.

The advantages of the use of CPAP in assisting stroke rehabilitation aregreater than that provided by oxygenation per se. For example, providingoxygen will in itself not prevent the patient from having an apnea.Reducing or eliminating apneas may reduce the damaging side-effects ofapnea, such as unnecessary activation of the sympathetic nervous system,surging blood pressure and increases in blood flow. Furthermore, someCPAP devices can detect the presence of apneas, distinguish betweencentral and obstructive apneas and provide an increased pressure ifneeded to stabilize an obstructed or partially obstructed airway.

Many stroke patients may be physically incapable of or experiencediscomfort in traveling to a sleep clinic for a sleep study. Hence thereis a need to provide alternative methods and apparatus for treating thebreathing disorders of stroke patients in rehabilitation. Furthermore,there are simply not enough places in sleep clinics to accommodatestroke patients. Thus in one aspect, the invention provides a simplifiedscreening, diagnosis and treatment models suitable for patients instroke rehabilitation which would not overburden the current sleepclinics.

In reference to FIG. 1, the invention provides apparatus that includes acomputer-controlled blower 2, flow and pressure sensors 4, a mask 6, airdelivery conduit 8 for connection between the blower 2 and the mask 6.The apparatus further includes a communication port or module 10, forexample, a wireless communication transceiver and/or a network card, forcommunication with other devices or computers such as hand-held displayand control devices 12. The apparatus further includes an oximeter inthe main blower housing. There is a sense tube 14 connected to the mainhousing of the blower to the mask which allows the apparatus to senseoxygen concentration and pressure levels in the mask 6. The apparatusfurther includes a communications interface 16 for connection to adiagnosis unit. The diagnosis unit includes a pulse oximeter 20,respiratory movement sensors 22, EEG & ECG 24.

While this apparatus is described as a single unit, it is understoodthat a combination of devices and/or computers linked by any availablecommunications method may be used to accomplish the goals of theinvention. For example, the apparatus can interface with a variety ofhand-held devices such as a Palm Pilot via wireless communication. Withsuch a device, a physician may, for example, remotely monitor, analyzeor record the status or data history of a patient or diagnose thepatient's condition using the device. For example, remote devices maystore stroke indicators, such as in a database of patient strokerecovery information for one or more patients, from data generated byuse of the apparatus. Furthermore, the treatment program which is beingrun on the patient can be monitored and changed remotely. In the eventpatient data is transmitted over open networks, the data may beencrypted for purposes of patient confidentiality.

The apparatus has two treatment modes, a first mode for treatingobstructive apneas and a second mode for treating central apneas. In thefirst mode, the device provides a generally constant pressure throughouta breathing cycle, but may vary the pressure in accordance withindications of partial or complete obstruction of the airway. Onetechnique for accomplishing this using a combination of flow limitationand snore measurements is described in U.S. Pat. No. 5,704,345(Berthon-Jones). One apparatus embodying aspects of the inventiondescribed in the '345 patent is AUTOSET T™ (ResMed Ltd). Other knownalternative methods to vary the pressure for delivering CPAP treatmentto a patient to treat obstructive apneas would be recognized by thoseskilled in the art and may be utilized as modes in the device.

In one form of the second mode, the apparatus provides a higher pressureto the mask during the inspiratory portion of the breathing cycle, theso-called IPAP, and a lower pressure to the mask during the expiratoryportion of the breathing cycle, the so-called EPAP. This may beaccomplished by monitoring the respiratory flow to the patient anddefining a threshold level. When flow exceeds the threshold then thedevice will deliver the IPAP, whilst below the threshold, the devicewill deliver the EPAP. The determination of respiratory airflow may beaccomplished by monitoring the total flow rate of air to the patient andsubtracting any components due to leak. Leak airflow may be determinedby using a method such as taught in U.S. Pat. No. 6,152,129(Berthon-Jones). Other known methods for determining leak may also beused by the device. The two different pressure levels may be achievedusing a least two methods. In one method, a near-constant speed blowerdevelops a constant pressure equivalent to the IPAP pressure and duringthe EPAP phase, some of the air is vented. In another method, a blowermay be alternately accelerated and decelerated in order to develop thepressure appropriate for each phase of the breathing cycle. The VPAP™ IIST/A (ResMed Ltd) uses the latter method.

In another form of the second mode, the device delivers therapy inaccordance with the methods taught in International Patent ApplicationWO 99/61088 (Berthon-Jones)

The apparatus according to the invention may be used to monitor patienthealth characteristics including, for example, oral and/or nasalairflow, snore, abdominal movement, chest wall movement, oximetry, pulserate, body position and flattening index via the diagnosis unit andsensors in the blower. As an alternative to the diagnosis unit apparatusaccording to the invention may be used in conjunction with a portablediagnosis system, for example, the EMBLETTA portable diagnosis system(FLAGA, Iceland), or the MESAM system (MAP, Germany). In a preferredembodiment, the flattening index is measured according to the methoddescribed in U.S. Pat. No. 5,704,345 (Berthon-Jones). The contents ofU.S. Pat. No. 5,704,345 are hereby incorporated by cross-reference.

The apparatus generates one or several indices determined from ananalysis of the patient's health characteristics useful for assessingappropriate treatment or diagnosing the condition of the patient. Suchindices serve as stroke indicators to indicate patient improvement orstroke type as detailed below. An index determined in accordance withthe invention may be used by a physician in conjunction with other knownmethods of analyzing the health of the patient. For example, an index inaccordance with the invention may be used in conjunction with acognitive test for assessing functional outcomes. In addition, an indexin accordance with the invention may be used to assess a patient inconjunction with Magnetic Resonance Imaging (MRI). The apparatus may beused to monitor a patient and generate an index with or without applyinga CPAP treatment regime.

One such index is based upon a functional relationship between thenumber of central or obstructive apneas over a particular time period.When the patient is being treated with CPAP, the device continuouslymonitors whether the patient is having an apnea and if so, whether theapnea is central or obstructive. The apparatus determines an index froma comparison of the number of central and obstructive apneas or afunction of the ratio of the number of central to obstructive apneasduring a particular time period.

Methods and apparatus for distinguishing between central and obstructiveapneas are described in U.S. Pat. No. 5,704,345. In one technique, whenan apnea is detected as occurring, the apparatus applies an oscillatorypressure waveform of known frequency and magnitude and accesses thepatency of the airway from the flow which is induced in the airway. Inone form, if the airway is patent during an apnea, then the apnea isjudged to be central. However, if the airway is closed during an apnea,then the apnea is judged to be obstructive. In another technique, whenan apnea is detected as occurring, the apparatus monitors the airflowfor the presence of a signal of cardiac origin. If a cardiac signal isdetected, then the airway is judged to be patent and the apneaclassified as central. If no cardiac signal is detected, then the airwayis judged to be closed and the apnea classified as obstructive.

Other methods for distinguishing between central and obstructive apneasinclude monitoring chest movement using respiratory bands and monitoringthe movement of the suprasternal notch, for example, as taught inInternational Patent Application WO 01/19433 (Berthon-Jones et al.).

This index may serve as an indication of the degree of neuro-recoveryfor a stroke patient. One effect of the stroke may be to damage thosecomponents of the brain which participate in respiratory drive, causinga relatively high incidence of central apneas compared to obstructiveapneas. If neuro-recovery causes the patient to recover some of thatrespiratory drive, there would be an impact on the index when comparedto an index recorded closer in time to the occurrence of stroke.

Alternatively, the effect of the stroke may be to damage brain tissueinvolved in the autonomic nervous system, which may cause a loss ofmuscle tone, for example to the airway. In turn this may lead to arelatively higher incidence of obstructive apneas. Hence the index maybe used as part of the assessment techniques to determine the type ofstroke which the patient has suffered. Use of the index may assist inassessing the location of the stroke, and in determining the appropriateform of therapy.

The changing value of the index may also provide an indication to thephysician that the dosage of pharmacological agents given to the patientought to be changed. For example, if the index indicated thatneuro-recovery was occurring, then it may be appropriate to reduce thedose of the agent. Alternatively, the index may be used to monitor theefficacy or effectiveness of a drug protocol. For example, by monitoringthe index for one or more patients, which may include the storing ofmultiple indices in a database of patient information, and by ananalysis of such data, it may be determined that a drug is safe and/orappropriate as a treatment for stroke in general. Additionally,monitoring and analysis may indicate that a particular treatment isworking for a particular patient.

The index may also be used as part of a CPAP-device management strategy.If a patient is being treated with a relatively more expensive computercontrolled CPAP device that is capable of treating both obstructive andcentral apneas, yet the index indicates that the patient has few centralapneas, then it may be appropriate to treat the patient with arelatively cheaper basic CPAP device which does not distinguish betweencentral and obstructive apneas.

An additional index may be a function of the pressure delivered to thepatient. In a computer controlled CPAP device such as ResMed Ltd.'sAUTOSET T™ which can automatically increase the CPAP pressure during anobstructive apnea to stabilize the airway, a record of the pressuresused to treat the patient may provide an indication of the changingstatus of the patient. For example, monitoring the 95th percentile ofpressure delivered during the previous treatment session, as describedin International Patent Application PCT/AU99/01130, may provide such astatus indication. Furthermore, an history of the 95th percentile of theprevious treatment session kept over several months may provide an indexof stroke recovery.

Neuro-recovery may result in an increase in upper airway muscle tonewhich in turn leads to a decrease in the CPAP pressure needed to treatan obstructive apnea. Monitoring the 95th percentile may be useful aspart of a CPAP-device management strategy. For example, if a patient isbeing treated with a relatively more expensive computer controlled CPAPdevice, yet the 95th percentile index indicates that there is littlechange in the pressure being delivered, it may be appropriate that thepatient be treated with a relatively cheaper basic CPAP device whichdelivers a fixed pressure.

Another index is an Apnea Hypopnea Index (“AHI”) which is an indicatorof the level of severity of a patient's sleep disordered breathing. TheAHI is determined by adding the total number of apneas and hypopneas thepatient experienced over a particular time period, such as during thestudy, and dividing that figure by the total time for that period. Anexample of an AHI scoring rule set is: (i) An apnea is scored if the2-second moving average ventilation drops below 25% of the recentaverage (time constant=100 s) for at least 10 consecutive seconds. (ii)An hypopnea is scored if the 8 second moving average drops below 50% butnot more than 25% of the recent average for 10 consecutive seconds.Other forms of AHI index are known by those skilled in the art.

The described apparatus may be used for the treatment and diagnosis ofstroke victims in accordance with the following protocol or programmedto follow a decision making protocol to provide automated assistance inthe process of evaluating the condition of and identifying appropriatetreatment for patients after stroke. A single device or multiple devicesmay be used to accomplish this protocol.

Patients typically enter rehabilitation clinics as a “stepping stone”between an acute care ward in a hospital and a return to normalcommunity life. The patients may come from stroke units, spinal units,respiratory wards or a number of other wards. Upon admission to arehabilitation clinic, the physician can conduct a sleep historyassessment of the patient with the questionnaire appearing on thehand-held device and the results being sent to the apparatus. Inconjunction with the assessment, the apparatus then may recommendparticular further tests to be done, such as oxygen saturation, andovernight sleep studies. The apparatus can conduct these tests andrecommend treatment levels. Further, the apparatus can provide CPAPtreatment.

There are a number of different patient treatment models which are shownas flowcharts in FIG. 2 to 6. The flow charts, and later discussion,indicate AutoSet T and VPAP as particular embodiments of the invention,however it is to be noted that in other forms of the invention, otherforms of CPAP and bi-level CPAP may be used. As part of the patienttreatment model, the apparatus can provide the physician with theappropriate healthcare reimbursement scheme codes.

In the first model, shown in FIG. 2, patients pass from acute care torehabilitation admission. According to the invention, all patientsentering the rehabilitation clinic are asked a number of simplequestions in a Sleep History Assessment, step 26, which are designed toprobe for the possibility of sleep disorders.

A set of possible questions is as follows:

-   -   Do you suffer from excessive daytime sleepiness?    -   Do you suffer from nocturnal choking?    -   Do you have restless sleep?    -   Do you snore? or Has anyone told you that you snore?    -   Do you stop breathing during sleep or has anyone ever told you        that you stop breathing during sleep ?    -   Do you suffer from a dry throat in the morning?    -   Do you suffer from headaches in the morning?    -   Do you feel very tired during the day?    -   Do you feel very sleepy during the day?    -   Have you ever fallen asleep while driving?        These questions are suitable for flagging the possibility that a        patient be given a more rigorous and detailed assessment by a        trained sleep or respiratory physician. A positive determination        indicates that an in-patient sleep study should be conducted.

During one form of sleep study such as by a portable device, thepatient's breathing is monitored. Their Apnea Hypopnea Index (AHI) isdetermined and each event is classified. Apneas can be classified asobstructive, central or mixed. Other events which can be identifiedinclude hypopneas, snoring & partial upper airway obstruction. Effort,position, oxygen saturation and flow limitation index can also bedetermined.

During a night of testing, step 28, patients with an Apnea HypopneaIndex (AHI) of greater than a threshold of about 20 are assessed todetermine if they have Central Sleep Apnea (CSA) or OSA. During acentral apnea, patients provide no respiratory effort. During anobstructive apnea, the patient's effort is obstructed by, for example,an overly flexible upper airway which physically blocks their attemptsat breathing. A patient may have both central and obstructive apneas ondifferent occasions. Those with OSA are given a night's assessment withan AUTOSET T™ apparatus to determine if treatment with that particulardevice is appropriate for the patient, step 30. This assessment is basedupon accepted medical standards for the use of the device. If thisassessment results in approval, the patient will be sent home with anAUTOSET T™ apparatus. Those patients diagnosed with CSA are assessedwith a bi-level CPAP device, step 32, such as the ResMed VPAP II ST/A.They are also given full polysomnography (PSG).

Patients with a negative result from the sleep history assessment aregiven a night's oxygenation screening using the apparatus. Thosepatients indicating a greater than 10% desaturation are given anin-patient portable sleep study as described above. Those patientsindicating a less than 10% desaturation are recommended routine care.

According to the clinical path shown in FIG. 3, the patient does notundergo sleep history assessment, otherwise, the path is similar to FIG.2. According to the clinical path shown in FIG. 4, patients diagnosedwith Central Sleep Apnea do not undergo full polysomnography, otherwisethe path is similar to FIG. 3.

The first out-patient clinical pathway is conducted in a sleeplaboratory after discharge from a rehabilitation hospital. As shown inFIG. 5, the patient is screened for Sleep Disordered Breathing (SDB) bymeasuring blood oxygenation overnight using apparatus according to theinvention. Those patients with a desaturation of less than 10% and anegative sleep history proceed to routine care. Those patients witheither a positive sleep history (for example, as determined via thequestioning indicated above) or a desaturation of greater than 10%proceed to a night study using the apparatus or alternatively, aportable device such as the EMBLETTA as described above.

Those patients with an AHI of less than a threshold of about 20 proceedto routine care. Those patients with an AHI of greater than about 20 areassessed to determine whether they have CSA or OSA. Those with OSA areassessed overnight with an AUTOSET T™ apparatus and full polysomnographyafter which they may be prescribed to take home the AUTOSET T™apparatus. Those patients with CSA are assessed with a VPAP apparatusand full polysomnography. They may then be prescribed with a VPAPapparatus. While the invention discloses 20 as a threshold, by recordingstroke indicators such as the AHI of many patients in a database andanalyzing other data for the patients, the threshold may be adjusted toimprove the accuracy of the threshold.

A second clinical pathway for out-patients is conducted in a sleeplaboratory prior to entry to a rehabilitation hospital. During the firstnight, the patient is screened for SDB using an oximeter. Those patientswith a desaturation of less than 10% and a negative sleep history passto routine care. Those patients with a greater than 10% desaturation ora positive sleep history indicating the possible presence of SDB thenpass to a night's full polysomnography. Those with an AHI of less than20 pass to routine care. Those with an AHI of greater than 20 areassessed to determine if they experience CSA or OSA. Those with CSA areassessed with a VPAP™ apparatus and may be discharged with the device.Those with OSA are assessed with an AUTOSET T™ apparatus and may bedischarged with the device.

Another aspect of the invention is that there is a follow-up for OSApatients of approximately 4 weeks after treatment using the AUTOSET T™apparatus. This period allows the patient to become more familiar withwearing the mask and breathing against the pressure. Importantly, sincein the AUTOSET T™ apparatus the device monitors patient compliance, theefficacy of treatment can be assessed. For example, the number hours ofpatient treatment including actual hours when the device was used andnot simply switched on can be reviewed by the clinic.

In a preferred embodiment, the apparatus identifies, displays and/orrecords reimbursement codes relating to the treatment provided by theapparatus. For example, the apparatus may be programmed to provide theappropriate US Medicare reimbursement codes indicated in FIG. 2 to thephysician via a hand-held device or other centralized computer to assistin the process of applying for funding of the treatment.

The Medicare codes which are provided for physician information by theapparatus, as shown on FIG. 2 to 6 are now described in more detail.ICD-9-CM coding is recommended for all clinical settings and is requiredfor reporting disease and diagnosis to all US public health services andHCFA programs. A physician needs to select the CPT code and descriptorthat most accurately identifies the procedure or service performed, andit may be provided by the apparatus. The physician may also listadditional procedures performed or pertinent special services and whennecessary, any modifier. All procedures and services need to beaccurately documented in the patient's medical record, which may beaccomplished through the communications module. The code may be subjectto a modifier. A modifier enables the reporting physician to indicatethat a performed service has been altered by some circumstance.Modifiers may be used to indicate: (a) a technical-only orprofessional-only component of services or procedures (e.g., 95810 TCindicates the technical-only component of a sleep study) and (b) that aservice or procedure was performed in part (e.g., 95810-52 indicates asleep study with a reduced number of channels recorded). Level Imodifiers are used in conjunction with Level I codes (CPT codes). Whenbilling CPT Code 95805, 95806, 95807, 95808, 95810, or 95811, anICD-9-CM code must be used.

FIG. 7 depicts an in-patient protocol in accordance with an embodimentof the invention. In accordance with the embodiment depicted in FIG. 7,a patient enters rehabilitation hospital in step 71. In step 72, a sleepdisordered breathing (SDB) questionnaire such as the one described aboveis given to the patient. The results of the questionnaire are reviewedby a physician in step 73. If the questionnaire provides a negativeassessment of SDB, and there is no suspicion of SDB, no furtherassessment of the patient takes place, as indicated in step 74. However,if the assessment indicates that there is a suspicion of SDB, furtherassessment is carried out, as indicated in step 77. In one form ofassessment, a portable diagnostic system, such as Embletta (Flaga,Iceland) is used as indicated by step 79(a). In another form ofassessment, full polysomnography (PSG) is carried out on the patient, asindicated in step 79(b). If either the portable or full diagnosis stepsprovides a negative result, as indicated in steps 78 and 80respectively, no further assessment of the patient is carried out.Following the flowchart line from the portable diagnostic system, ifthere is a positive outcome from the assessment, (step 81) a trial of anautomatically titrating CPAP device, such as AutoSet T, is provided asindicated in step 83. This is given a review at four weeks, as indicatedin step 86. If the SDB is resolved, treatment with the automaticallytitrating CPAP device is discontinued. If the SDB does not resolve,treatment with a fixed pressure CPAP or an automatically titrating CPAPdevice is continued as indicated in step 89. In addition, in step 90,the patient is followed up in a CPAP clinic as appropriate. Followingthe flowchart line from a positive full polysomnography, a full CPAPtitration study is carried out in step 85. A patient may then go on to afixed pressure CPAP or an automatically titrating CPAP, such as AutoSetT. In common with the flowchart path from a portable diagnostic system,a patient following the full PSG diagnosis will be followed up in a CPAPclinic as appropriate. Steps 79 to 90 may be managed by a sleep servicefacility.

While the invention has been described in one form, it is to beunderstood that this form is merely illustrative of the invention. Forexample, it is contemplated that a device in accordance with anembodiment of the invention conducts monitoring during a monitoringperiod of a patient without delivering air at positive pressure. In thisembodiment, a device may include an airflow monitor, such as an airflowsensor, a respiratory effort monitor, such as a respiratory band orsuprasternal notch sensor, and a computer programmed to calculate thenumber of central and obstructive apneas from data from the airflow andrespiratory effort monitors and derive a stroke indicator therefrom.Those skilled in the art would understand that the stroke indicator maybe calculated using data from the monitoring period. Furthermore, thestroke indicator may be calculated at a location remote from themonitoring device. Other variations can be made without departing withthe spirit and scope of the invention.

1. A method for evaluating the condition of a patient after strokecomprising the steps of: delivering breathable gas at a pressure aboveatmospheric to a patient after stroke; measuring the airflow of saidpatient; and determining, using a computer, a stroke indicator from saidairflow, said stroke indicator representing information about thepatient's stroke condition.
 2. The method of claim 1 wherein saiddetermining step includes analyzing said airflow to determine anoccurrence of central apnea and said stroke indicator is calculated as afunction of said occurrence of central apnea.
 3. The method of claim 2wherein said determining step includes analyzing said airflow todetermine an occurrence of obstructive apnea and said stroke indicatoris calculated as a function of said occurrence of obstructive apnea. 4.The method of claim 1 further comprising the step of evaluating changesin said stroke indicator to assess the efficacy of an administered drug.5. The method of claim 4 wherein said step of evaluating said strokeindicator includes storing said stroke indicator in a database ofpatient information.
 6. The method of claim 5 wherein said strokeindicator is a function of a number of occurrences of central apnea. 7.The method of claim 6 wherein said stroke indicator is a function of anumber of occurrences of obstructive apnea.
 8. A method for evaluatingthe condition of a patient after stroke in accordance with claim 1further comprising the steps of: determining the number of central andobstructive apneas which the patient has during a first time period; andcalculating a stroke indicator index from a comparison of the number ofcentral and obstructive apneas which the patient has during the firsttime period, said stroke indicator representing information about thepatient's rehabilitation from stroke.
 9. An apparatus for evaluating thecondition of a patient after stroke comprising: a source for deliveringbreathable gas at a pressure above atmospheric to a patient afterstroke; a sensor for measuring the airflow of said patient; and meansfor determining a stroke indicator from said airflow, said strokeindicator representing information about the patient's stroke condition.10. An apparatus for evaluating the condition of a patient after strokein accordance with claim 9 wherein said determining means analyzes saidairflow to determine occurrences of central apneas and said strokeindicator is determined as a function of said occurrences of centralapneas.
 11. An apparatus for evaluating the condition of a patient afterstroke in accordance with claim 10 wherein said determining meansanalyzes said airflow to determine occurrences of obstructive apneas andsaid stroke indicator is determined as a function of said occurrences ofobstructive apneas.
 12. An apparatus for evaluating the condition of apatient after stroke in accordance with claim 9 wherein said determiningmeans further evaluates changes in said stroke indicator to assess theefficacy of an administered drug.
 13. An apparatus for evaluating thecondition of a patient after stroke in accordance with claim 12 whereinsaid determining means further stores the evaluated stroke indicator ina database of patient information.
 14. An apparatus for evaluating thecondition of a patient after stroke in accordance with claim 13 whereinsaid stroke indicator is evaluated as a function of a number ofoccurrences of central apneas.
 15. An apparatus for evaluating thecondition of a patient after stroke in accordance with claim 14 whereinsaid stroke indicator is evaluated as a function of a number ofoccurrences of obstructive apneas.
 16. An apparatus for evaluating thecondition of a patient after stroke in accordance with claim 9 furthercomprising effort sensor means for measuring the respiratory effort ofthe patient; and wherein said determining means monitors the airflow andeffort sensor means to determine a number of central and obstructiveapneas which the patient has during a first time period, and calculatessaid stroke indicator from a comparison of the number of central andobstructive apneas which the patient has during the first time period,said stroke indicator representing information about the patient'srecovery from stroke.
 17. The apparatus for evaluating the condition ofa patient after stroke in accordance with claim 16 wherein the effortsensor means is a respiratory band.